Amphibian chytrid fungus reaches
Madagascar
26 February 2015
amphibian breeding stations and developing
probiotic treatments, say the scientists, writing in
Scientific Reports, the acclaimed open-access
journal from the publishers of Nature.
The entire amphibian class is currently afflicted by
a global pandemic that is accelerating extinction at
an alarming rate. Although habitat loss caused by
human activity still constitutes the main threat to
amphibian populations, habitat protection no longer
provides any guarantee of amphibian survival.
Infectious diseases are now threatening even
seemingly secluded habitats. The most devastating
of the known amphibian diseases is
chytridiomycosis, which is caused by a deadly
chytrid fungus (Batrachochytrium dendrobatidis, or
Bd). The fungus attacks the skin, which is
particularly important in amphibians because they
breathe through it. A large number of species have
already been lost in this way - particularly in tropical
Boophis quasiboehmei is from the Ranomafana National Central America, where two-thirds of the colourful
Park in Southeast Madagascar. Credit: Miguel Vences / harlequin frog species have already been
decimated across their entire area of distribution.
TU Braunschweig
Bd has now been identified in over 500 amphibian
species, 200 of which have seen a significant
decline in numbers. The pathogen is therefore
classified worldwide as one of the greatest threats
The chytrid fungus, which is fatal to amphibians,
has been detected in Madagascar for the first time. to biodiversity.
This means that the chytridiomycosis pandemic,
which has been largely responsible for the
decimation of the salamander, frog and toad
populations in the USA, Central America and
Australia, has now reached a biodiversity hotspot.
The island in the Indian Ocean is home to around
290 species of amphibians that are not found
anywhere else in the world. Another 200 frog
species that have not yet been classified are also
thought to live on the island. Researchers from the
Helmholtz Centre for Environmental Research
(UFZ) and TU Braunschweig, together with
international colleagues, are therefore proposing
an emergency plan. This includes monitoring the
spread of the pathogenic fungus, building
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amphibians may have developed resistance to it.
However, further research is needed to confirm this
Chytrid fungus was proved on Platypelis pollicaris from
hypothesis before the all-clear can be given. It is
Ranomafana. Credit: Miguel Vences / TU Braunschweig also possible that the fungus was brought to the
island in crustaceans or the Asian common toad
(Duttaphrynus melanostictus), carried in by
migratory birds or humans. "Luckily, there have not
Until now, however, a few islands like Madagascar yet been any dramatic declines in amphibian
were thought not to have been affected. The last
populations in Madagascar," Dirk Schmeller
series of tests from 2005 to 2010 found no trace of reports. "However, the pathogen appears to be
the pathogenic fungus there. However, an analysis more widespread in some places than others.
of the latest series of tests shows that the chytrid
Madagascar may have several strains of the
fungus also poses a threat to amphibians in
pathogen, maybe even the global, hypervirulent
Madagascar. "This is sad news for amphibianstrain. This shows how important it is to be able to
lovers around the world," says Dr Dirk Schmeller of isolate the pathogen and analyse it genetically,
the UFZ, who was involved in analysing the
which is something we haven't yet succeeded in
samples. "Firstly, it means that an island that is
doing." At the same time, the researchers
home to a particularly high number of amphibian
recommend continuing with the monitoring
species is now at risk. Several hundred species live programme across the entire country to observe
only on this island. And, secondly, if the pathogen the spread of the disease. The scientists also
has managed to reach such a secluded island, it
suggest setting up extra breeding stations for key
can and will occur everywhere."
species, in addition to the two centres already
being built, to act as arks, so that enough
For the study that has just been published, the
amphibians could be bred to recolonise the habitats
research team analysed samples from over 4000
in a crisis. "We are also hopeful that we may be
amphibians from 50 locations in Madagascar taken able to suppress the growth of the Bd pathogen
since 2005. Samples from four species of
with the help of skin bacteria," says Miguel Vences.
Madagascan frog (Mantidactylus sp.) taken in
"It might then be possible to use these bacteria as a
2010, and from one Mascarene frog (Ptychadena kind of probiotic skin ointment in the future." A high
mascareniensis) taken in 2011 from the remote
diversity of microbial communities in the water
Makay massif tested positive for the fungus. In
could also reduce the potential for infection,
samples from 2013 and 2014 the pathogen was
according to earlier investigations conducted by
found in five different regions. Prof. Miguel Vences UFZ researchers and published in Current Biology.
from TU Braunschweig says, "The chytrid fungus
was found in all four families of the indigenous
The outbreak of amphibian chytridiomycosis in
Madagascan frogs, which means it has the
Madagascar puts an additional seven per cent of
potential to infect diverse species. This is a shock!" the world's amphibian species at risk, according to
The study also shows that the disease affects
figures from the Amphibian Survival Alliance (ASA).
amphibians at medium to high altitudes, which ties "The decline in Madagascan amphibians is not just
in with observations from other parts of the world, a concern for herpetologists and frog researchers,"
where the effects of the amphibian epidemic have says Dr Franco Andreone from the International
been felt primarily in the mountains.
Union for Conservation of Nature (IUCN), who is
one of the study authors. "It would be a great loss
The fact that the fungus has been identified in a
for the entire world." In the coming months, the
very remote part of the island has puzzled the
scientists therefore plan to work with the
researchers. There is some hope that it may prove government to draw up an emergency plan to
to be a previously undiscovered, native strain of the prevent this scenario.
pathogen, which may have existed in the region for
some time and have gone undetected because of a More information: Sci. Rep. 5, 8633; DOI:
lack of samples. In this case, Madagascar's
10.1038/srep08633
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Provided by Helmholtz Association of German
Research Centres
APA citation: Amphibian chytrid fungus reaches Madagascar (2015, February 26) retrieved 16 June
2017 from https://phys.org/news/2015-02-amphibian-chytrid-fungus-madagascar.html
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